During the processing of semiconductor wafers used in manufacturing integrated circuits and the like, it is often necessary to clean the wafer. One process for cleaning semiconductor wafers is to immerse them in a liquid chemical of a desired composition. The liquid may be stirred or otherwise caused to flow across or against the surfaces of the wafers to provide an effective surface cleaning action. Wet cleaning processes are used to remove various metallic, organic, and particulate contaminants. The wet chemistries are also employed to remove native oxide layers from the wafer surface. The liquid-based cleaning techniques, however, have some limitations. For instance, wet chemistries cannot be easily integrated with other device fabrication processes in a cluster tool environment. Moreover, they may introduce additional contaminants onto the wafers. Additional problems include extensive usage and disposal of chemicals as well as the related environmental considerations. As a result, some vapor-phase processes have been developed which can replace wet chemistries for selected applications such as native oxide removal. However, no viable and proven vapor-phase chemistries exist for effective removal of all the surface contaminants.
One known vapor-phase system that attempts to remove surface particulates use an excimer laser beam to scan the semiconductor wafer. U.S. Pat. No. 4,987,286 to Susan D. Allen and assigned to the University of Iowa Research Foundation, issued Jan. 22, 1991, (hereinafter "Allen" describes a method and apparatus for removing minute particles (as small as sub-micron particles) from a surface to which they adhere. An energy transfer medium is interposed between each particle to be removed and the surface to which the particles adhere. The medium is then irradiated with laser energy at a wavelength which is strongly absorbed by the medium. The medium absorbs sufficient energy to cause explosive evaporation with sufficient force to dislodge the particles. That method and system, however, requires scanning the semiconductor device and has two significant drawbacks.
One limitation of Allen is that by having to scan the semiconductor wafer with the smaller laser beam, throughput of this cleaning method is limited. Excimer lasers are expensive and require significant maintenance costs to operate. This makes the scanning procedure a time consuming and expensive procedure. Another limitation is that the scanning itself may cause local thermal stresses that adversely affect the physical characteristics and performance of the semiconductor device. Also, another limitation is that the method of the Allen is only applicable to particulate removal.
Consequently, there is a need for an improved method for removing particulates and other contaminants from semiconductor wafers that avoids the use of expensive laser devices, and that provides more effective removal of both particulates and other contaminants.
There is a need for a method and system that permit particulate removal and substrate cleaning with a condensed-phase processing environment.
There is a need for a method and system that provide both pre-process and post-process particulate removal and surface cleaning in a semiconductor wafer fabrication reactor that uses condensed-phase processing.
There is a further need for a method and system can be easily integrated with cluster tool platforms in order to reduce manufacturing cycle time and enhance fabrication yield.